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Aqueous Preparations
Syrups are commonly used aqueous preparations. Syrup is a solution of water and sugar to which a drug is added. Addition of flavoring agents eliminates the bitter taste of many drugs.

Alcoholic Preparations
Elixirs, spirits, tinctures, and fluid extracts are drugs dissolved in various concentrations of alcohol, usually in the range of 5 to 20 percent.

Solid and Semisolid Preparations
The solid type of preparation is most common. A number of different kinds for different purposes are available.

Powders
Powders are drugs or drug extracts that are dried and ground into fine particles.

Tablets
Tablets are drug powders that have been compressed into a convenient form for swallowing. They usually disintegrate in the stomach more rapidly than most other solid preparations.

Troches and Lozenges
These flattened tablets are allowed to dissolve in the mouth. They are commonly used for colds and sore throats.

Capsules
Gelatin capsules are used to administer drug powders or liquids. Gelatin capsules dissolve in the stomach, thereby releasing the drug.

Delayed-Release Products
These are usually tablets or capsules that are treated with special coatings so that various portions of the drug will dissolve at different rates. Delayed-release products usually contain the equivalent of two or three single-dose units. They are designed to produce drug effects over an extended time.

Enteric-Coated Products
Some drugs are very irritating to the stomach. Also, the gastric juices of the stomach can inactivate certain drugs. In these cases, the drug tablet or capsule is coated with an acid-resistant substance that will dissolve only in the less acidic portions of the intestines. Enteric-coated products should be taken on an empty stomach with water, either 1 hour before or 2 hours after meals.

Suppositories
These are drugs mixed with a substance (cacao butter) that will melt at body temperature. Suppositories are intended for insertion into the rectum, urethra, or vagina.

Ointments
Ointments or salves are soft, oily substances (petrolatum or lanolin) containing a drug that is applied to the skin or, in the case of ophthalmic ointments, to the eye.

Transdermal Products
Transdermal products are administered through a bandage or patch system. The drug is released from the bandage or patch and is then absorbed through the skin into the systemic circulation. This method provides a continuous source of the drug over 24 hours or more.
Nitroglycerin, estrogen, and clonidine are drugs available in this form.

Parenteral Injection
Parenteral injection involves the administration of drugs by needle and syringe. Different injection sites such as subcutaneous (SC), intramuscular (IM), intravenous (IV), and others provide different rates of drug absorption and onset of action. Parenteral injection requires the practice of sterile technique and various safety precautions.

Bioavailability: percentage of the drug dosage that is absorbed.

Drug absorption: entrance of a drug into the bloodstream from its site of administration.

Drug addiction: condition of drug abuse and drug dependence that is characterized by compulsive drug behavior.

Drug dependence: condition of reliance on the use of a particular drug, characterized as physical and/ or psychological dependence.

Drug distribution: passage of a drug from the blood to the tissues and organs of the body.

Drug excretion: elimination of the drug from the body.

Drug metabolism: the enzymatic biotransformation of a drug into metabolites.

Drug microsomal metabolizing system (DMMS): group of enzymes located primarily in the liver that function to metabolize (biotransformation) drugs.

Drug tolerance: decreased drug effect occurring after repeated drug administration.

Enzyme induction: increase in the amount of drug-metabolizing enzymes after repeated administration of certain drugs

Enzyme inhibition: inhibition of drug-metabolizing enzymes by certain drugs.